Because I think that measuring according impedance to faber's YOUTUBE and other sources seemed to me rather complicated, I made my own (short) description.
This describes step by step 'how to' setup and measure the impedance of loudspeakers.
You will find a setting for low impedances and for 100 V systems.
I packed all the cabling, switches and resistors in a junction box. This prevents much fiddling with the cables.
Unfortunately the file is 1.4 MB large so it exceeds the upload limit.
Because of forum restrictions I can't upload the in this file mentioned EXCEL calculation too.
Therfore I will give you a link to download both in a folder.https://app.seafile.de/d/228b11ea0d/
After working with 2 FFT I find this app really really great!
...At my page you might find another interesting article:http://members.aon.at/ernstgenser/Artikel/prediction_of_soundlevel_in_offices_eng.pdf